Engine degradation management via multi-engine mechanical power control

ABSTRACT

A multi-engine power system is described that includes at least a first engine and a second engine configured to jointly provided mechanical power to the multi-engine power system. The multi-engine power system further includes a controller configured to estimate a deterioration factor of the first engine. The controller is further configured to adjust, based on the deterioration factor of the first engine, a first amount of mechanical power being provided by the first engine to increase a service time of the first engine, and adjust, based on the first amount of mechanical power being provided by the first engine, a second amount of mechanical power being provided by the second engine to compensate for the adjustment to the first amount of mechanical power.

This application is a continuation of U.S. application Ser. No.15/586,136 filed May 3, 2017, which claims the benefit of U.S.Provisional Application Ser. No. 62/333,747 filed May 9, 2016, both ofwhich are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The disclosure relates to techniques for mechanical power management inmulti-engine systems.

BACKGROUND

Some systems rely on multiple engines for producing mechanical power.For example, many aircraft (e.g., fixed-wing, rotorcraft,tilt-rotorcraft, etc.) rely on two or more engines to produce thrust.Mechanical deterioration and operational stresses endured by mechanicalcomponents of an engine may cause performance of that engine to degradeover time. Even if a multi-engine system commands each engine to provideapproximately the same amount of mechanical power, each engine isinherently unique and may degrade at a different rate.

Eventually an engine may degrade to its respective end-of-life. Althoughother engines of the system may still possess useful life, a system mayneed to be taken offline each time a degraded engine needs to beserviced, overhauled, or replaced. To avoid having to take an entiresystem offline each time a single engine needs overhauling or replacing,a multi-engine system may replace all the engines while the system isoffline, potentially wasting the useful life left in the other enginesthat do not necessarily need replacing.

SUMMARY

In one example, the disclosure is directed to an engine controller thatincludes at least one processor, and a memory storing instructions. Theinstructions, when executed, cause the at least one processor to:estimate a deterioration factor of a first engine from two or moreengines that are configured to jointly provide mechanical power to amulti-engine power system, adjust, based on the deterioration factor ofthe first engine, a first amount of mechanical power being provided bythe first engine to extend a service time of the first engine, andadjust, based on the first amount of mechanical power being provided bythe first engine, a second amount of mechanical power being provided bya second engine from the two or more engines to compensate for theadjustment to the first amount of mechanical power.

In another example, the disclosure is directed to a method that includesestimating, by a controller of two or more engines of a multi-enginepower system, a deterioration factor of a first engine from two or moreengines that are configured to jointly provide mechanical power requiredby the multi-engine power system, and adjusting, by the controller,based on the deterioration factor of the first engine, a first amount ofmechanical power being provided by the first engine to increase aservice time of the first engine. The method further includes adjusting,by the controller, based on the first amount of mechanical power beingprovided by the first engine, a second amount of mechanical power beingprovided by a second engine from the two or more engines to compensatefor the adjustment to the first amount of mechanical power.

In yet another example, the disclosure is directed to a multi-enginepower system that includes at least a first engine and a second engineconfigured to jointly provided mechanical power to the multi-enginepower system, and a controller. The controller is configured to:estimate a deterioration factor of the first engine, adjust, based onthe deterioration factor of the first engine, a first amount ofmechanical power being provided by the first engine to increase aservice time of the first engine, and adjust, based on the first amountof mechanical power being provided by the first engine, a second amountof mechanical power being provided by the second engine to compensatefor the adjustment to the first amount of mechanical power.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages of the disclosure will be apparent from the description anddrawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram illustrating an example multi-enginesystem configured to independently adjust the mechanical power beingprovided by multiple engines to balance the respective degradationlevels of each of the engines, in accordance with one or more aspects ofthe present disclosure.

FIG. 2 is a flow chart illustrating example operations performed by anexample controller configured to individually adjust the mechanicalpower being provided by multiple engines to balance the respectivedegradation levels of each of the engines, in accordance with one ormore aspects of the present disclosure.

FIG. 3 is a conceptual diagram illustrating degradation rates of twodifferent engines of an example multi-engine system that is configuredto independently adjust the mechanical power being provided by multipleengines to balance the respective degradation levels of each of theengines, in accordance with one or more aspects of the presentdisclosure.

DETAILED DESCRIPTION

In general, techniques and circuits of this disclosure may enable anengine controller to individually adjust the mechanical power beingprovided by two or more engines of a multi-engine system to adjust thedegradation rate of at least one of the engines while meeting mechanicalpower requirements of the system. For example, a multi-engine system,such as an aircraft, may rely on mechanical power provided by two ormore engines (e.g., turbine engines, piston engines, etc.) to providethrust, to be converted to electrical power, or the like. An examplecontroller of the multi-engine system may dynamically manage themechanical power output from each of the two or more engines not only tomeet the mechanical power requirements of the system, but also todirectly affect deterioration of mechanical components of, and thereforedegradation in performance of, at least one of the engines. In otherwords, unlike other multi-engine system controllers that manage engineoutput primarily to satisfy electrical or mechanical power requirementsof the system, the example controller described herein also considersengine degradation when determining how much mechanical power to extractfrom each engine at any given time.

For instance, the example controller may request different amounts ofmechanical power from two different engines depending on the degradationlevels of the two engines. The controller may keep the total powerproduced by the two engines the same, while commanding the betterpreforming (or less deteriorated) engine of the two to produce morepower and commanding the worse performing (or more deteriorated) engineof the two to produce less power. The power differential between the twoengines may depend on the difference in degradation between them.

In this way, the example controller may vary mechanical power producedby at least one engine in the system as a way to manage the relativedeterioration and degradation of each engine in the system, extend theservice time or even end-of-life of a more deteriorated engine, or causemultiple engines to degrade a different rates so as to be ready forservice at approximately the same time. In addition, since a betterperforming engine (e.g., an engine that produces more mechanical powerfor similar degradation rate) typically consumes less fuel than a worseperforming engine, a multi-engine system that relies on an examplecontroller described herein may experience better overall fuel flowsince the example controller may cause the better performing engine toproduce more of the mechanical power. As such, a multi-engine systemthat relies on the example controller may experience less down time,have a greater maintenance-free operating period, potentially consumeless fuel, and therefore, cost less to operate and maintain as comparedto other systems.

FIG. 1 is a conceptual diagram illustrating an example multi-enginesystem 100 configured to adjust the mechanical power being provided bymultiple engines to balance the respective degradation levels of each ofthe engines, in accordance with one or more aspects of the presentdisclosure. Multi-engine system 100 (also referred to simply as “system100”) represents any multi-engine system relies on two or more enginesfor mechanical power. For ease of description, system 100 is describedprimarily as being part of an aircraft, such as a fixed-wing aircraft,rotor-craft, tilt-rotor craft or any other type of aircraft. However,many other examples of system 100 exist. For example, system 100 may bepart of a mechanical power system of a marine craft, space craft, orother vehicle, a power plant for driving generators for powering a powergrid or other electrical system, or any other type of mechanical powersystem that relies on the mechanical output from multiple engines toperform work.

System 100 includes engines 102A-102N (collectively “engines 102”),mechanical shafts 108A-108N (collectively “shafts 108”), one or moreloads 106, and controller 112. Controller 112 is communicatively coupledto some or all of components 102, 106, and 108 via communication link118. In other examples, system 100 may include additional or fewercomponents than those shown including a single communication link 118 ormultiple, communication links communicatively coupling controller 112 tothe various components of system 100.

Loads 106 represent any number of components (e.g., mechanical orelectrical) that rely on mechanical power produced by a multi-enginepower system such as system 100. For example, when system 100 is part ofan aircraft, load 106 may include any quantity electrical machines(e.g., alternators, generators, or other electrical machines) forpowering lighting components, avionics components, pumps, communicationsystems, computer systems, display systems, cabin comfort systems, orany other electrical component or subsystem of the aircraft. Load 106may include any quantity of mechanical propulsion components (e.g.,shafts, propellers, gearboxes, or other mechanical components) that relyon mechanical power from a multiple engines to perform work. As oneexample, loads 106 are shown in FIG. 1 as propellers, however loads 106may include any type of and any quantity of mechanical load that derivesmechanical power from one or more engines such as engines 102.

Loads 106 are shown in FIG. 1 as being mechanically coupled to engines102 via mechanical shafts 108. When engine 102A is running, engine 102Amay output mechanical power to loads 106 by spinning mechanical shaft108A. Similarly, when engine 102N is running, engine 102N may outputmechanical power to loads 106 by spinning mechanical shaft 108N.

Each of engines 102 represents any mechanical power source that isconfigured to produce mechanical power. In some examples, engines 102may produce mechanical power for loads 106, for instance, for providingthrust or power for one or more propellers, fans, fuel pumps, hydraulicpumps and other equipment associated with load 106. As shown in FIG. 1,each of engines 102 may be mechanically coupled to a propeller or fan(e.g., a propulsor) for producing thrust. Examples of engines 102include gas turbine engines, internal combustion engines, such as pistonor rotary engines, or any other type of engine that mechanically drivesone or more mechanical shafts 108. The mechanical output from each ofengines 102 can be individually controlled by controller 112. Forexample, controller 112 may control the throttle of engine 102A tocontrol the speed at which engine 102A spins mechanical shaft 108Aindependently of the throttle setting controller 112 commands to engine102N to control the speed with which engine 102N spins mechanical shaft108N.

In some examples, for instance, on a multi-engine aircraft, each engine102 may include multiple shafts 108. For example, in examples in whichengine 102 are gas turbine engines, often times each of engines 102 mayhave two shafts, a high pressure shaft and a low pressure shaft. Load106 may be coupled to one or both shafts 108 to receive mechanical powerbeing produced by engines 102.

In any case, by load 106 consuming mechanical power from engines 102,load 106 is extracting mechanical power from the thermodynamic cycles ofengines 102. This mechanical power extraction by load 106 will affectthe thermodynamic cycle of each of engines 102 thereby impacting fuelconsumption, operating temperatures, and pressures in each of engines102.

Each of engines 102 may be at a different stage in its respectiveservice time or life cycle when that engine is installed in system 100.For example, engine 102N may be been installed in system 100 as a newengine, hours, months or even years before engine 102A is installed as anew engine in system 100. Therefore, when engine 102A is installed insystem 100, engine 102A may inherently have a longer remaining operatinglife as compared to engine 102N since engine 102N was installed and ranfor some time prior to engine 102A being installed. Or in some examples,engines 102A and 102N may be installed as new engines in system 100 atthe same time, but engine 102N may incur damage or experience a failurecondition (e.g., during combat, training, or in an accident) and as aresult, have a shorter respective service time or life cycle as comparedto engine 102A that did not incur damage or experience the failurecondition.

Even if each of engines 102 are at the same stage in their respectiveservice times or operating life cycles when installed in system 100, andeach of engines 102 has similar power and torque ratings, each ofengines 102 is unique and the respective performance of each may degradeat different rates over time. For example, due to variations inmanufacturing conditions, operating conditions, environmentalconditions, and other factors, the mechanical components of engine 102Amay deteriorate faster than the mechanical components of engine 102N.Engine 102A may therefore be required to work harder (e.g., run faster,hotter, etc.) during its life to produce the same amount of mechanicalpower as engine 102N. Eventually, over time, even if both engines 102Aand 102N are controlled so as to produce the same or similar amounts ofmechanical power, engines 102A and 102N may reach their respective endof life or service time, at different points in time. For example,engine 102A may degrade or deteriorate more quickly than engine 102N andneed to be maintained, overhauled, and/or replaced before engine 102Nneeds similar servicing.

In general, controller 112 may control the amount of mechanical powerbeing produced by each of engines 102 for use by load 106 and the restof system 100. Controller 112 may adjust the mechanical power beingprovided by engines 102 to manage the rate of degradation of at leastone of engines 102 while meeting mechanical power requirements of system100.

Controller 112 is shown in FIG. 1 as being operationally coupled to eachof components 102, 106, and 108 via communication link 118, which may beone or more wired or wireless communication links. In some examples,controller 112 may be operationally coupled to a subset of components102, 106, and 108. Controller 112 may exchange information acrosscommunication link 118 between components 102, 106, and 108, and anyother components of system 100 to cause engines 102 to distribute, andrefrain from distributing, mechanical power to load 106. In someinstances, controller 112 may communicate via communication link 118with other control modules of system 100 (not shown in FIG. 1), such asrespective engine control modules associated with engines 102, to varyor manage the mechanical power being produced for load 106.

Controller 112 may comprise any suitable arrangement of hardware,software, firmware, or any combination thereof, to perform thetechniques attributed to controller 112 herein. Examples of controller12 include any one or more microprocessors, digital signal processors(DSPs), application specific integrated circuits (ASICs), fieldprogrammable gate arrays (FPGAs), or any other equivalent integrated ordiscrete logic circuitry, as well as any combinations of suchcomponents. When controller 121 includes software or firmware,controller 112 further includes any necessary hardware for storing andexecuting the software or firmware, such as one or more processors orprocessing units.

In general, a processing unit may include one or more microprocessors,DSPs, ASICs, FPGAs, or any other equivalent integrated or discrete logiccircuitry, as well as any combinations of such components. Although notshown in FIG. 1, controller 112 may include a memory configured to storedata. The memory may include any volatile or non-volatile media, such asa random access memory (RAM), read only memory (ROM), non-volatile RAM(NVRAM), electrically erasable programmable ROM (EEPROM), flash memory,and the like. In some examples, the memory may be external to controller112 (e.g., may be external to a package in which controller 112 ishoused).

While controller 112 may coordinate mechanical power production anddegradation of engines 102 to meet overall performance requirements(e.g., total electrical, mechanical, and/or thrust power) of system 100,controller 112 may also control engines 102 to coordinate deteriorationor degradation in performance of engines 102 as a way to coordinate therespective service life of each of engines 102. For example, controller112 may control engines 102 to ensure a total amount of thrust orparticular fuel consumption is being provided by engines 102 while atthe same time request a different amount of power from each of engines102 depending on their respective degradation levels. For instance,controller 112 may request less power from a more degraded engine 102and to compensate in the total system level reduction in power,controller 112 may request more power from a lightly degraded engine102. By controlling engines 102 based on the respective deteriorationlevels of each of engines 102, controller 112 may coordinate therespective service times of engines 102.

As used herein, the term “service time” of an engine corresponds to anymilestone in the life cycle of an engine at which it may be desirable toreplace, perform maintenance, overhaul, repair, or otherwise service theengine. For example, the service time of an engine may correspond to theend-of-life of the engine or a maintenance milestone of the engine.

The service time of an engine may depend on a variety of factors,including variations in: manufacturing conditions of the engine andcomponents thereof (e.g., variations in quality, humidity, materials,etc.), operating stresses (e.g., throttle settings, torque settings,operating temperatures, acceleration loads, other stresses, etc.)environmental conditions (e.g., altitude variations, externaltemperature variations, humidity variations, etc.) and other factors(e.g., bird strikes, combat related damage, civilian accidents,maintenance or operator error, etc.).

The service time of an engine may occur naturally (e.g., through regularuse) or occur suddenly (e.g., after a failure event) and may change overtime. For instance, the service time of an engine that was previouslyset to occur at some future time may change and correspond to an earliertime (e.g., due to stressing the engine, bird strike, combat event,accident, etc.). In some examples, the service time of an engine thatwas previously set to occur at some future time may change and becomeimmediate, corresponding to a current time (e.g., due to a catastrophicfailure event from combat, accident, over-stressing, other failurecondition).

Controller 112 may operate with an objective of managing deteriorationlevels of engines 102 such that each of engines 102 reaches a respectiveservice time at approximately the same time. For example, controller 112may extract mechanical power from each engine 102 differently, asneeded, to decrease the rate of degradation of the most degraded engine102 (less electrical power extraction) while increasing the rate ofdegradation of the least degraded engines 102 (more electrical powerextraction). By adjusting mechanical power extraction from engines 102based on deterioration levels of engines 102, controller 112 mayminimize the frequency with which system 100 goes down for enginemaintenance and in some examples, may extend the amount of time betweenengine service times. In addition, by extracting more mechanical powerfrom a less deteriorated engine 102 to compensate for a reduction inmechanical output from a greater deteriorated engine 102, controller 112may cause system 100 to have an overall reduced amount of fuel flow. Assuch, the example multi-engine system may experience less down time forengine maintenance and cost less to maintain as compared to othersystems.

FIG. 2 is a flow chart illustrating example operations performed by anexample controller configured to adjust the mechanical power beingprovided by multiple engines to balance the respective degradationlevels of each of the engines, in accordance with one or more aspects ofthe present disclosure. FIG. 2 is described in the context of thecomponents of system 100 of FIG. 1, although the technique of FIG. 2 maybe implemented by other systems including additional or fewercomponents. Controller 112 may perform additional or fewer operationsthan those shown in FIG. 2 and may perform the operations shown in FIG.2 in any order.

As shown in FIG. 2, in accordance with techniques of this disclosure,controller 112 may estimate a deterioration factor of a first engine anda deterioration factor of a second engine from two or more engines thatare configured to jointly provide mechanical power to a multi-enginepower system (200). For example, controller 112 may communicate via link118 with load 106 and the various other systems and subsystemsassociated with system 100 to determine the total mechanical powerrequired from engines 102. Controller 112 may determine the totalmechanical power to be provided to load 106 and system 100 so thatcontroller 112 can cause engines 102 to jointly provide sufficientmechanical power to system 100.

While controller 112 causes engines 102 to jointly provide mechanicalpower that is sufficient to power load 106, controller 112 may monitorone or more operating parameters associated with each of engines 102 inorder to estimate respective deterioration factors associated with eachof engines 102. For example, controller 112 may monitor operatingtemperatures, fuel consumption rates, shaft speeds, hours of usage,pressures, amounts of electrical and mechanical output, and otheroperating parameters associated with engines 102 to obtain informationabout the respective degradation levels of each of engines 102 in orderto quantify an amount of remaining useful life associated with each ofengines 102.

Controller 112 may measure the one or more respective operatingparameters associated with engines 102 over prior time durations (e.g.,one or more minutes, hours, and/or days of prior operation) and inputthe measured operating parameters into a model for estimating,predicting, or projecting the amount of degradation of each of engines102 or the amount of useful life left in each of engines 102 until itsnext service time. For example, controller 112 may rely on a model thatis built from prior engine data collected over time for a particular oneof engines 102, or from other, similar engines. The model may projectthe current performance of a particular engine onto a degradation glideslope that the model uses to estimate an end-of-life, or other servicetime of that particular engine. The model may determine a deteriorationfactor (e.g., a percentage, a score, etc.) that indicates an amount ofdegradation or amount of operating life that has been used up by aparticular one of engines 102, before that particular one of engines 102will fail, need replacing, or otherwise need servicing. Controller 112may rely on look up tables, functions, or other modules (in addition toor instead of a model) to determine the deterioration factor of aparticular one of engines 102.

Unlike other engine balancing control systems, the example multi-enginesystem may rely on averaging techniques and/or trends analysis in thedeterioration data to determine the best mechanical power output toextract from each engine at various times. In addition, unlike otherengine balancing control systems, the example multi-engine system mayperform engine-life management optimization rather than engine-limitavoidance. In other words, rather than simply control engines to avoidexceeding their mechanical power limits, the example multi-engine systemmay perform trend analysis of engine data to control when and how fastan engine reaches the end of its useful life.

Although primarily described herein as indicating an engine's amount(e.g., percentage) of degradation or an amount of spent or consumeduseful life, a deterioration factor in some examples could insteadindicate an amount of life that is left in an engine. In cases where thedeterioration factor indicates an engine's amount of degradation oramount of spent or consumed useful life, reducing mechanical output fromthat engine may reduce the rate of increase of the deterioration factorof the engine. Whereas, in cases where the deterioration factorindicates and engine's remaining useful life, reducing mechanical outputfrom that engine may reduce the rate of decrease of the deteriorationfactor of the engine.

Controller 112 may input one or more operational parameters of engines102A into the model, and in response, the model may output adeterioration factor of engines 102A. Similarly, controller 112 mayinput one or more operational parameters of engines 102N into the model,and in response, the model may output a deterioration factor of engines102N. For instance, the model may output a deterioration factor ofengine 102A that corresponds to a percentage of a total amount ofdegradation of engine 102A before engine 102A requires servicing or atotal amount of degradation of engine 102A since engine 102A was lastserviced. Similarly, the model may output a deterioration factor ofengine 102N that corresponds to a percentage of a total amount ofdegradation of engine 102N before engine 102N requires servicing or atotal amount of degradation of engine 102N since engine 102N was lastserviced.

Controller 112 may rely on various sensors embedded within engines 102and other parts of system 100 to determine the deterioration factor ofeach of engines 102. For example, controller 112 may communicate withspeedometers, tachometers, accelerometers, thermometers, pressuresensors, and the like to determine whether the performance of each ofengines 102 has degraded, and if so, by how much.

In some examples, the model relied on by controller 112 may equateturbine temperature at a certain power to a deterioration factor. Forinstance, if the temperature of engine 102A is higher than expected fora certain commanded output, the model may determine that by running hot,engine 102A is degraded. The level of temperature increase over expectedmay be proportional to the amount of degradation of the engine.

Controller 112 may measure variations in fuel flow to achieve certainpower as indicators of a deterioration factor of one of engines 102. Forexample, controller 112 may determine that a higher than expected rateof fuel burn for a particular power setting indicates that a particularengine 102 is more degraded than a different engine that burns less fuelfor the same particular power setting.

Similar to temperature and fuel flow, controller 112 may determine adeterioration factor of any one of engines 102 based on shaft speed ofthat particular one of engines 102 to achieve certain power output. Forexample, controller 112 may determine that a higher than expected shaftspeed of shaft 108A for a particular power setting indicates that engine102A is more degraded than engine 102N which spins shaft 108N at a lowershaft speed for the same particular power setting.

Controller 112 may determine a differential between the deteriorationfactor of the first engine and the deterioration factor of the secondengine (210). For example, controller 112 may refrain from balancing theservice times of two or more engines 102 if the deterioration factorsare too far apart (e.g., the difference in deterioration factors exceedsa threshold) and only coordinate the service times if the deteriorationfactors are somewhat similar (e.g., the difference in deteriorationfactors is less than the threshold).

Controller 112 may determine whether the differential exceeds athreshold (220). For instance, controller 112 may refrain fromcoordinating service times if engine 102A is greatly deteriorated (e.g.,having degraded by 80% and having only 20% remaining life) and engine102N is less deteriorated (e.g., having degraded by only 10% and stillhaving 90% remaining life) causing the differential betweendeterioration factors of engines 102A and 102N to be high (e.g.,approximately 70%). On the other hand, if engine 102A is somewhatdeteriorated (e.g., having degraded 50% and having 50% remaining life),and engine 102N is less deteriorated (e.g., having degraded 80% and onlyhaving 20% remaining life), causing the differential betweendeterioration factors of engines 102A and 102N to be approximately 30%,controller 112 may coordinate services times of engines 102A and 102N.

Responsive to determining that the differential exceeds a threshold(220, YES path), controller 112 may refrain from adjusting the firstamount of mechanical power being provided by the first engine. Forexample, controller 112 may avoid adjusting the mechanical power beingprovided by engines 102A and 102N to balance service times if thedifference in deterioration factors is too great (e.g., greater than50%).

Conversely, controller 112 may adjust the first amount of mechanicalpower being provided by the first engine (230) in response todetermining that the differential does not exceed the threshold (220, NOpath) and may adjust, based on the first amount of mechanical powerbeing provided by the first engine, a second amount of mechanical powerbeing provided by the second engine to compensate for the adjustment tothe first amount of mechanical power (240). For example, controller 112may decrease the amount of mechanical power being provided by engine102A to decrease a rate of change in the deterioration factor of engine102A (e.g., to extend the service life of engine 102A) or may increasethe amount of mechanical power being provided by engine 102A to increasea rate of change in the deterioration factor of the engine 102A (e.g.,to shorten the service life of engine 102A). In any case, whethercontroller 112 increases or decreases the power output from engine 102A,controller 112 may adjust the power output of engine 102N to compensatefor the adjustment to 102A such that system 100 continues to receive therequired amount of mechanical power form engines 102. In other words, ifcontroller 112 decreases the power output from engine 102A by someamount, controller 112 may increase the power output from engine 102N bya similar amount.

In some examples, controller 112 may adjust the amount of mechanicalpower being provided by engine 102A in response to determining a rate ofchange in the deterioration factor of engine 102A exceeds a rate ofchange in a deterioration factor of engine 102N. Said differently,controller 112 may perform operations 200-240 in response to determiningthat engine 102A may be deteriorating faster than engine 102N whichcauses the deterioration factor of engine 102A to increase more rapidlythan deterioration factor of engine 102N. For example, while controller112 may estimate the deterioration factors of engines 102A and 102N tobe approximately 50%, controller 112 may determine that thedeterioration factor of engine 102A suddenly increases to 90% (e.g.,after suffering from catastrophic component failure, combat damage, birdstrike, or experiencing some other failure condition) while thedeterioration factor of engine 102N only increases slightly above 50%.Controller 112 may determine that the sudden change in deterioration ofone engine but not the other requires management to extend the servicelife of all of engines 102.

While the above example has been described from the perspective ofengine 102A, similar operations may be performed against engine 102N orany other one of engines 102. For example, controller 112 may adjust theamount of mechanical power being provided by engine 102A in response todetecting a change in the deterioration factor of engine 102N. Forinstance, while controller 112 may estimate the deterioration factors ofengines 102A and 102N to be approximately 50%, controller 112 maydetermine that the deterioration factor of engine 102N suddenlyincreases to 90% while the deterioration factor of engine 102A continuesto remain at approximately 50%.

Although in some examples, controller 112 may adjust mechanical outputfrom engines 102 to extend the service life of one or more of engines102, in other instances, controller 112 may deliberately burn up orshorten the service time of one of engines 102 (e.g., a good engine) tomatch the service life of that engine 102 with a badly deterioratedengine 102. For example, system 100 may experience a failure condition(e.g., due to damage from combat, damage from a bird strike, or someother failure condition) causing engine 102A to change from having adeterioration factor of 50% to having a deterioration factor of 90%. Toprevent engine 102A from deteriorating further, controller 112 maydramatically increase the power being commanded from engine 102N tocause the deterioration factor of engine 102N to catch-up with thedeterioration factor of engine 102A. While holding, or at leastminimizing the increase in the deterioration factor of engine 102Abeyond 90%, controller 112 may control the power output from engine 102Nto cause the deterioration factor of engine 102N to increase from 50% to90% even though engine 102N did not experience the failure conditionthat engine 102A experienced.

FIG. 3 is a conceptual diagram illustrating degradation rates of twodifferent engines of an example multi-engine system that is configuredto adjust the mechanical power being provided by multiple engines tobalance the respective degradation levels of each of the engines, inaccordance with one or more aspects of the present disclosure. FIG. 3 isdescribed below in the context of system 100 of FIG. 1 as well asoperations 200-240 of FIG. 2.

FIG. 3 includes degradation glide slopes 300A and 300B of engine 102Aand degradation glide slopes 302A and 302B of engine 102N. As shown inFIG. 3, both engines 102A and 102N are “100% healthy” at time t0 or atleast at the same degradation level. At time t0, controller 112 maydetermine that both engines 102A and 102N have approximately the same,respective deterioration factors that correspond to approximately 0%indicating that neither of engines 102A or 102N has degraded. In somecases, engines 102A and 102N may be newly installed engines of system100, newly overhauled, etc.

In any case, during operational use, engine 102N may degrade faster thanengine 102A. For example, as illustrated by a comparison betweendegradation glide slopes 300A and 302A between times t0 and t1, eitherdue to manufacturing differences or other characteristics that makeengine 102A unique from engine 102N, engine 102N may degrade faster thanengine 102A causing the deterioration factor of engine 102A to increaseat a faster rate than the rate of increase of the deterioration factorof engine 102N. At time t1, controller 112 may estimate that engine 102Ahas a deterioration factor of 50% whereas engine 102N has adeterioration factor of 70% and if left unchecked, engine 102N willdegrade to a 100% deterioration factor at time t2 and engine 102A willdegrade to a 100% deterioration factor at time t4.

Rather than continue to cause engines 102A and 102N to evenly split thepower required by system 100, controller 112 may alter its mechanicalpower control scheme associated with engines 102 to compensate for thedifferences in degradation glide slopes 300A and 302A, and to coordinatethe service times of engines 102A and 102N. For example, controller 112may increase the amount of mechanical power being extracted from engine102A so as to increase the rate at which the deterioration factor ofengine 102A increases, thereby causing engine 102A to degrade faster andaccording to degradation glideslope 300B. Controller 112 may decreasethe amount of mechanical power being extracted from engine 102N so as tocause engine 102N to degrade slower and according to degradationglideslope 302B thereby decreasing the rate at which the deteriorationfactor of engine 102N increases. In this way, controller 112 may causeengines 102A and 102N to continue to satisfy the mechanical power needsof system 100 while causing engines 102A and 102N to reach theirrespective service times at approximately the same time (e.g., at timet3).

In one or more examples, the operations described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the operations may be stored on or transmitted over, as oneor more instructions or code, a computer-readable medium and executed bya hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media, which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transient media, but areinstead directed to non-transient, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore DSPs, general purpose microprocessors, ASICs, FPGAs, or otherequivalent integrated or discrete logic circuitry. Accordingly, the term“processor,” as used herein may refer to any of the foregoing structureor any other structure suitable for implementation of the techniquesdescribed herein. In addition, in some aspects, the functionalitydescribed herein may be provided within dedicated hardware and/orsoftware modules. Also, the techniques could be fully implemented in oneor more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a processor, an integrated circuit(IC) or a set of ICs (e.g., a chip set). Various components, modules, orunits are described in this disclosure to emphasize functional aspectsof devices configured to perform the disclosed techniques, but do notnecessarily require realization by different hardware units. Rather, asdescribed above, various units may be combined in a hardware unit orprovided by a collection of interoperative hardware units, including oneor more processors as described above, in conjunction with suitablesoftware and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. An engine controller comprising: at least oneprocessor; and a memory storing instructions that, when executed, causethe at least one processor to: monitor one or more operating parametersof each of a first engine and a second engine from two or more enginesthat are configured to jointly provide mechanical power to amulti-engine power system; estimate a deterioration factor of the firstengine based on the one or more operating parameters of the firstengine, wherein the first engine is configured to supply mechanicalpower to a first propulsor or a first generator; estimate adeterioration factor of the second engine based on the one or moreoperating parameters of the second engine, wherein the second engine isconfigured to supply mechanical power to a second propulsor or a secondgenerator, different from the first propulsor or the first generator;adjust, based on the deterioration factor of the first engine, a firstamount of mechanical power being provided by the first engine to extenda service time of the first engine; and adjust, based on thedeterioration factor of the second engine, a second amount of mechanicalpower being provided by the second engine to at least partiallycompensate for the adjustment to the first amount of mechanical power.2. The engine controller of claim 1, wherein the one or more operatingparameters of the first engine includes at least one of a temperature ofthe first engine, a fuel consumption of the first engine, or a shaftspeed of the first engine, and wherein the one or more operatingparameters of the second engine includes at least one of a temperatureof the second engine, a fuel consumption of the second engine, or ashaft speed of the second engine.
 3. The engine controller of claim 1,wherein the instructions, when executed, further cause the at least oneprocessor to: estimate the deterioration factor of the first engineusing a model that equates the one or more operating parameters of thefirst engine at the first amount of mechanical power to thedeterioration factor of the first engine; and estimate the deteriorationfactor of the second engine using a model that equates the one or moreoperating parameters of the second engine at the second amount ofmechanical power to the deterioration factor of the second engine. 4.The engine controller of claim 1, wherein the instructions, whenexecuted, further cause the at least one processor to: adjust the firstamount of mechanical power being provided by the first engine to adjusta rate of change of the deterioration factor of the first engine; adjustthe second amount of mechanical power being provided by the secondengine to adjust a rate of change of the deterioration factor of thesecond engine.
 5. The engine controller of claim 4, wherein theinstructions, when executed, further cause the at least one processorto: adjust the first amount of mechanical power being provided by thefirst engine to decrease the rate of change of the deterioration factorof the first engine to extend the service time of the first engine; andadjust the second amount of mechanical power being provided by thesecond engine to increase the rate of change of the deterioration factorof the second engine to shorten a service time of the second engine. 6.The engine controller of claim 5, wherein the instructions, whenexecuted, further cause the at least one processor to: determine thatthe rate of change of the deterioration factor of the first engine isgreater than the rate of change of the deterioration factor of thesecond engine; in response to determining that the rate of change of thedeterioration factor of the first engine is greater than the rate ofchange of the deterioration factor of the second engine, adjusting thefirst amount of mechanical power being provided by the first engine andthe second amount of mechanical power being provided by the secondengine.
 7. The engine controller of claim 1, wherein the deteriorationfactor of the first engine corresponds to a percentage of a total amountof degradation of the first engine, and wherein the deterioration factorof the second engine corresponds to a percentage of a total amount ofdegradation of the second engine.
 8. A method comprising: monitoring, bya controller of two or more engines that are configured to jointlyprovide mechanical power to a multi-engine power system, one or moreoperating parameters of each of a first engine and a second engine ofthe two or more engines: estimating, by the controller, a deteriorationfactor of the first engine based on the one or more operating parametersof the first engine, wherein the first engine is configured to supplymechanical power to a first propulsor or a first generator; estimating,by the controller a deterioration factor of the second engine based onthe one or more operating parameters of the second engine, wherein thesecond engine is configured to supply mechanical power to a secondpropulsor or a second generator, different from the first propulsor orthe first generator; adjusting, by the controller and based on thedeterioration factor of the first engine, a first amount of mechanicalpower being provided by the first engine to extend a service time of thefirst engine; and adjusting, by the controller and based on thedeterioration factor of the second engine, a second amount of mechanicalpower being provided by the second engine to at least partiallycompensate for the adjustment to the first amount of mechanical power.9. The method of claim 8, wherein the one or more operating parametersof the first engine includes at least one of a temperature of the firstengine, a fuel consumption of the first engine, or a shaft speed of thefirst engine, and wherein the one or more operating parameters of thesecond engine includes at least one of a temperature of the secondengine, a fuel consumption of the second engine, or a shaft speed of thesecond engine.
 10. The method of claim 8, further comprising:estimating, by the controller, the deterioration factor of the firstengine using a model that equates the one or more operating parametersof the first engine at the first amount of mechanical power to thedeterioration factor of the first engine; and estimating, by thecontroller, the deterioration factor of the second engine using a modelthat equates the one or more operating parameters of the second engineat the second amount of mechanical power to the deterioration factor ofthe second engine.
 11. The method of claim 8, further comprising:adjusting, by the controller, the first amount of mechanical power beingprovided by the first engine to adjust a rate of change of thedeterioration factor of the first engine; and adjusting, by thecontroller, the second amount of mechanical power being provided by thesecond engine to adjust a rate of change of the deterioration factor ofthe second engine.
 12. The method of claim 11, further comprising:adjusting, by the controller, the first amount of mechanical power beingprovided by the first engine to decrease the rate of change of thedeterioration factor of the first engine to extend the service time ofthe first engine; and adjusting, by the controller, the second amount ofmechanical power being provided by the second engine to increase therate of change of the deterioration factor of the second engine toshorten a service time of the second engine.
 13. The method of claim 8,wherein the deterioration factor of the first engine corresponds to apercentage of a total amount of degradation of the first engine, andwherein the deterioration factor of the second engine corresponds to apercentage of a total amount of degradation of the second engine.
 14. Amulti-engine power system comprising: at least a first engine and asecond engine configured to jointly provide mechanical power to themulti-engine power system; and a controller configured to: monitor oneor more operating parameters of each of the first engine and the secondengine; estimate a deterioration factor of the first engine based on theone or more operating parameters of the first engine, wherein the firstengine is configured to supply mechanical power to a first propulsor ora first generator; estimate a deterioration factor of the second enginebased on the one or more operating parameters of the second engine,wherein the second engine is configured to supply mechanical power to asecond propulsor or a second generator, different from the firstpropulsor or the first generator; adjust, based on the deteriorationfactor of the first engine, a first amount of mechanical power beingprovided by the first engine to extend a service time of the firstengine; and adjust, based on the deterioration factor of the secondengine, a second amount of mechanical power being provided by the secondengine to at least partially compensate for the adjustment to the firstamount of mechanical power.
 15. The multi-engine power system of claim14, wherein the one or more operating parameters of the first engineincludes at least one of a temperature of the first engine, a fuelconsumption of the first engine, or a shaft speed of the first engine,and wherein the one or more operating parameters of the second engineincludes at least one of a temperature of the second engine, a fuelconsumption of the second engine, or a shaft speed of the second engine.16. The multi-engine power system of claim 14, wherein the controller isconfigured to: estimate the deterioration factor of the first engineusing a model that equates the one or more operating parameters of thefirst engine at the first amount of mechanical power to thedeterioration factor of the first engine; and estimate the deteriorationfactor of the second engine using a model that equates the one or moreoperating parameters of the second engine at the second amount ofmechanical power to the deterioration factor of the second engine. 17.The multi-engine power system of claim 14, wherein the controller isconfigured to: adjust the first amount of mechanical power beingprovided by the first engine to adjust a rate of change of thedeterioration factor of the first engine; and adjust the second amountof mechanical power being provided by the second engine to adjust a rateof change of the deterioration factor of the second engine.
 18. Themulti-engine power system of claim 17, wherein the controller isconfigured to: adjust the first amount of mechanical power beingprovided by the first engine to decrease the rate of change of thedeterioration factor of the first engine to extend the service time ofthe first engine; and adjust the second amount of mechanical power beingprovided by the second engine to increase the rate of change of thedeterioration factor of the second engine to shorten a service time ofthe second engine.
 19. The multi-engine power system of claim 14,wherein the deterioration factor of the first engine corresponds to apercentage of a total amount of degradation of the first engine, andwherein the deterioration factor of the second engine corresponds to apercentage of a total amount of degradation of the second engine. 20.The multi-engine power system of claim 14, wherein the first and secondengines are tilt-rotor engines of a tilt-rotor aircraft.